The present invention relates to the field of mass storage devices. More particularly, this invention relates to magnetoresistive (xe2x80x9cMRxe2x80x9d) heads used in a disc drive.
Many disc drives today use a transducer formed of two elements. A first element is a thin film head that is used for writing information representative of data to the surface of the memory disc. A second element is a magnetoresistive element or giant magnetoresistive element (xe2x80x9cMR elementxe2x80x9d) that is used to read information representative of data from the surface of the memory disc. The resistance of the MR element changes in the presence of a magnetic field so the MR element is used to sense transitions on the disc that have been previously written with the thin film write element. The transducer is typically housed within a small ceramic block called a slider. The slider is passed over the rotating disc in close proximity to the disc that includes magnetic transitions representative of data.
The process of forming individual sliders starts with forming multiple transducers on a surface of a ceramic wafer using semiconductor fabrication techniques. After forming the transducers on the wafer, the wafer is then sliced or cut to form an elongated bar having a row of transducers, also known as a rowbar. The row of transducers are positioned on the trailing edge of the rowbar. One aspect of the transducer is known as a magnetoresistive (MR) read element which consists of a stack of materials known as a stripe. The response of the MR transducer to the presence of a magnetic field is a change in resistance (delta R/R). The static resistance of the MR element is a critical dimension of reader performance and is a function of the stripe height. As a result, manufacturing includes removal of material to produce a stripe height that produces a head with a certain specified resistivity. During manufacture, the elongated rows of transducers are placed in carriers and material is removed by abrasive lapping to provide the specified stripe height via removal of material.
The initial steps of forming the MR elements on the wafers using semiconductor device fabrication techniques does not produce MR elements having uniform stripe heights. After the wafer has been sliced into rowbars lapping is used to both expose a cross-section of the reader stripe to the slider surface and to control the final MR stripe height. The MR stripe height is monitored during lapping by resistance feedback control. The removal of material from the sliced wafer or row of ceramic material by lapping removes about the same amount of material from every MR element associated with a row of MR elements. The result is that the resistivity of the MR elements varies significantly across the row of MR elements sliced from the ceramic wafer. In other words, the methods for removing material from a row of MR elements held on a holder treats each MR element in the row uniformly. This results in a wide distribution of stripe heights and a wide distribution of resistivity associated with the individual MR elements across the row of MR elements.
Still another problem associated with the MR element manufacturing process is that feedback as to the stripe height or resistivity of individual MR elements generally is not obtained during the lapping portion of the manufacturing process. Thus, the accuracy of determining stripe height or any parameter related to the stripe height is limited. This may result in a significant deviation or offset between the targeted and the actual value for stripe height.
Measuring and monitoring the cleanliness endpoint of a rowbar is also important. This entails monitoring the first derivative of resistance versus time (dR/dt). MR elements which do not incorporate this processing technique may become electrically ineffective due to the presence of material such as dead oxide layers and organic surface contamination or extraneous metal.
What is needed is a method and apparatus that can be used to carefully control the rate of material removal in forming the stripe height dimension and controllably remove extraneous material when it exists on individual MR elements within a row of MR elements. What is also needed is a method and apparatus for feedback control so that the stripe height and any related operating parameter can be controlled during manufacture of the MR elements. The combination of the aforementioned features into a process that narrows the distribution of the MR elements such that more of the elements have a selected stripe height or selected operating parameter. What is also needed is a method and apparatus that is both reliable and quick, such that it can be used to produce MR elements in large volume.
Another aspect of the transducer is the writer element. The writer element is fabricated on the wafer simultaneously with the MR element. After the rowbar is formed, the pole tip of the writer element may be recessed or protruding. If the pole tip is protruding, then it may contact the recording media, which would cause damage to the media and the pole tip. If the pole tip is recessed too far into the head, data will not be able to be written. Therefore, there is a need for a method and apparatus that evaluates and corrects the length of the pole tip as it relates to the air bearing surface.
As mentioned above, the transducer is processed onto the slider and the slider carries the transducer over the recording media. As the density of data tracks on the media continues to increase, increased efficiency of the magnetic read/write head is required. The trailing edge of sliders are positioned closer and closer to the recording media in order to ensure an accurate signal both to and from the transducer. As a result, the slider occasionally comes into contact with the recording media, which poses the problem of damaging the media and the slider. Thus, there is a need for a method and apparatus to measure and monitor a slider with a trailing edge, to process the trailing edge so that if it does contact the media, minimal damage will occur.
The present invention addresses these and other needs to this and other problems, and offers other advantages over current systems and devices.
A method for producing magnetoresistive heads that enables the individual adjustment of the dimension of selected property levels of the transducer to a specified or targeted level with improved accuracy and precision. The method of stripe height formation involves the exposure of MR transducers at the rowbar level of fabrication to a focused ion beam for sputter removal of material. An electrical property, generally the resistance associated with the MR stripe, of the MR element is monitored until the resistance reaches a desired level and the focused ion beam is blanked or deflected. This method may also be used to control the cleanliness endpoint of the MR element, the pole tip of the write element and the trailing edge of the slider.
The next MR element in the sequence of transducers along a rowbar, namely a second MR element, is exposed to the focused ion beam and its resistance is monitored during material removal by ion sputtering until the resistance endpoint is reached. This sequence of in situ resistance monitoring, sputter etching until endpoint, and moving to the next transducer along a rowbar is repeated until the rowbar is fully processed. Using this process, the resistivity of individual MR elements within the rowbar can be tightly controlled.
A method for producing magnetoresistive heads includes the steps of placing a rowbar having multiple magnetoresistive elements in an environment which includes a focused ion beam. The focused ion beam is directed onto a first area of the rowbar that includes a single, individual magnetoresistive element while a property level of the single, individual magnetoresistive element is monitored. The property is monitored while the focused ion beam acts on the single, individual magnetoresistive element. When the property level reaches a desired level, the focused ion beam is redirected onto a second area of the rowbar that includes a second single, individual magnetoresistive element. The process of monitoring the property level as the focused ion beam acts on the second magnetoresistive element until the property level reaches a desired level is repeated. All of the magnetoresistive elements are treated individually. Monitoring the property level includes the step of measuring the electrical resistance or other property of the magnetoresistive elements in situ to the ion sputtering environment.
Redirecting the focused ion beam onto successive areas of the rowbar includes placing the rowbar on a stage. The stage is moved so the focused ion beam is directed onto the successive area of the rowbar. Each area which receives individual treatment eventually becomes the trailing edge area of a slider.
A controller must be used to coordinate the processes of device measurement with material removal by ion etching. One way of measuring the electrical properties of each device is via probe contact. The first step in the process is for the controller to move the stage to the position of a first device. Electrical probes are then engaged so the resistivity of the transducing elements can be monitored by the controller. The focused ion beam is unblanked or otherwise directed to an area including a first transducing element and etching of that transducing element occurs until feedback related to the desired electrical property reaches a selected level. The focused ion beam is then deflected or blanked by the controller and the probe contact is removed from the first device. The controller increments the stage to a position corresponding to the second device and the series of process steps is repeated by the controller.
Advantageously, the method and apparatus allows for careful control of the dimensions of a transducer/slider so that the resistivity, cleanliness endpoint, pole tip of the writer element, and the trailing edge of the slider are tightly controlled. Since the property levels of the transducer/slider are tightly controlled, the signal output and the functional efficiency of the slider/transducer are within a selected, optimized range for most of the slider/transducers in a manufactured population. The focused beam, an electrical probe apparatus and electronic controls form a control loop that tightly control the process. The method and apparatus are reliable, such that the method and apparatus can be used in production of transducers and sliders for disc drives. A result of the ability to tightly control a particular critical dimension of the transducer and slider are that disc drives using these magnetic read-write recording heads enable higher aerial density information storage. Another advantage is that the yield of MR elements in a rowbar is improved due to tightened sigma values. Sigma values, or the standard deviation of the of the transducer elements, represent greater precision in manufacturing. Thus, higher capacity disc drives may be introduced because of this technology and disc drives capable of still further increases in storage capacity can be produced at the manufacturing level.
These and various other features as well as advantages which characterize the present invention should be apparent to those skilled in the art upon reading the following detailed description.